The 'Wallonian Saga' has illustrated a number of structural weaknesses of the European Union as an external treaty-maker in the field of EU Common Commercial Policy that concern issues of both democratic representation and effectiveness of EU multilevel governance. The legal question of competence that determines the Union’s power to conclude external commercial treaties by itself or, in the alternative, jointly with the member states will be clarified by the CJEU in its forthcoming judgement in Opinion 2/15. We provide an overview of the relevant CJEU case law and the main issues that arose during the Court’s hearing in the Opinion 2/15 procedures; discuss the law and practice of the provisional application of international treaties by the EU and legal avenues that enable the entry into force of a mixed agreement despite its rejection by an individual member state. We argue in favour of adjusting the scope of future EU trade and investment agreements to the realm of EU exclusive competences as clarified by the CJEU to remedy the functional deficiencies of EU treaty-making that were exposed in the ‘CETA-drama’. At the same time, we emphasize the need for – and outline a path towards – a qualitative change in EU and member state institutional practice that fully employs the channels of vertical political participation in the Union’s multilevel governance structures so as to strengthen the legitimacy of EU economic treaty-making.